System and method for improved auto-boating

ABSTRACT

According to one embodiment of the invention, a system used in auto-boating includes a tape substrate supported by a boat. The tape substrate includes a pair of lateral edges parallel to one another and each having respective first and second ends, and a pair of longitudinal guide strips parallel to one another. One of the longitudinal guide strips extends between the respective first ends of the pair of lateral edges and the other longitudinal guide strip extends between the respective second ends of the pair of lateral edges. The tape substrate also includes a plurality of die attach regions disposed within the area defined by the pair of lateral edges and the pair of longitudinal guide strips. The system further includes a boat clip coupled to the boat such that the tape substrate is sandwiched between the boat and the boat clip. Each longitudinal guide strip includes a pair of tabs disposed at opposite ends thereof such that each tab extends beyond a respective one of the lateral edges.

This patent application claims priority from U.S. patent applicationSer. No. 10/719,616, filed 21 Nov. 2003, the entirety of which areincorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to the field of integrated circuit packaging and,more specifically, to a system and method for improved auto-boating.

BACKGROUND

Because of the sheer volume of integrated circuits in the marketplace,packaging of integrated circuits in a manner that is cost-effective withhigh yield is important for semiconductor manufacturers in order thatthey can be competitive in the marketplace. One important process in thefabrication of integrated circuits is the die attach process. Because ofthe ever decreasing thickness of some substrates, such as tapesubstrates, the die attach process becomes even more important becauseof the challenges present when attaching die to these types ofsubstrates.

The auto-boating process, which sandwiches a tape substrate between aboat and a clip, greatly enhances the die attach process for tapesubstrates. However, since the clip holds down only a very small stripof the substrate along its edges, the possibility of the substrate edgesgetting jammed with the clip windows at the ends of the clip is highbecause of the coiling effect when placing a tape substrate on a boat.This leads to substrate bowing and warping along its edges, which meansthat the integrated circuit dies formed along the edges of the tapesubstrate may have to be scrapped, which hurts yield.

SUMMARY

According to one embodiment of the invention, a system used inauto-boating includes a tape substrate supported by a boat. The tapesubstrate includes a pair of lateral edges parallel to one another andeach having respective first and second ends, and a pair of longitudinalguide strips parallel to one another. One of the longitudinal guidestrips extends between the respective first ends of the pair of lateraledges and the other longitudinal guide strip extends between therespective second ends of the pair of lateral edges. The tape substratealso includes a plurality of die attach regions disposed within the areadefined by the pair of lateral edges and the pair of longitudinal guidestrips. The system further includes a boat clip coupled to the boat suchthat the tape substrate is sandwiched between the boat and the boatclip. Each longitudinal guide strip includes a pair of tabs disposed atopposite ends thereof such that each tab extends beyond a respective oneof the lateral edges.

Some embodiments of the invention provide numerous technical advantages.Other embodiments may realize some, none, or all of these advantages.For example, protrusions at the four comers of a tape substrate createsmall extensions at the edges of the tape substrate, which substantiallyeliminates the possibility of contact between the edges of the tapesubstrate and the clip windows. Hence, the tape substrate slides inplace when the clip is pushed downward onto the tape substrate and anybowing/warping along the edges of the tape substrate is eliminated.These protrusions may easily be fabricated onto the edges of the tapesubstrate without having to change the length of the tape from whichtape substrates are formed.

Other technical advantages are readily apparent to one skilled in theart from the following figures, descriptions, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the invention, and for furtherfeatures and advantages, reference is now made to the followingdescription, taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is an exploded perspective view of a boat and a clip sandwichinga tape substrate according to one embodiment of the present invention;

FIG. 2 illustrates the bowing of a prior art tape substrate beingsandwiched between a boat and a clip; and

FIGS. 3A and 3B are plan views of a tape substrate according to oneembodiment of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Example embodiments of the present invention and their advantages arebest understood by referring now to FIGS. 1 through 3B of the drawings,in which like numerals refer to like parts.

FIG. 1 is an exploded, perspective view of a system 100 utilized in anauto-boating process according to one embodiment of the presentinvention. The auto-boating process is well known in the integratedcircuit fabrication industry. Hence, all details of such a process maynot be fully described herein. Generally, system 100 is utilized in thefabrication of integrated circuits, such as ball grid arrays (“BGAs”).In the illustrated embodiment, system 100 includes a boat 102, a boatclip 104, and a tape substrate 106 disposed therebetween. Tape substrate106 has a plurality of die attach regions 108 in which integratedcircuit die are coupled thereto in order to fabricate individualintegrated circuits.

Generally, boat 102 is used as a carrier for tape substrate 106 duringthe fabrication of integrated circuits and boat clip 104 secures tapesubstrate 106 to boat 102. Boat clip 104 facilitates the die attachprocess for tape substrate 106 by including a plurality of windows 110formed therein that expose die attach regions 108 on tape substrate 106.Both boat 102 and boat clip 104 may be formed from any suitablematerial; however, boat 102 and boat clip 104 are typically formed froma suitable metal.

Because tape substrate 106 is typically very thin, boat 102 and boatclip 104 are needed to secure tape substrate 106 in place so thatintegrated circuit die may be attached to tape substrate 106 in anaccurate and cost-efficient manner. As a brief example of thefabrication process for integrated circuits utilizing system 100,integrated circuit die (not shown) are attached to respective die attachregions 108 on tape substrate 106, a suitable wire bonding processcouples the integrated circuit die to the appropriate contacts on eachdie attach region 108, and then tape substrate 106 is transferred to thenext assembly station so that a suitable encapsulation process may takeplace. After encapsulation, a suitable ball attach process is utilizedto attach solder balls to the underside of a tape substrate 106 beforethe integrated circuits are singulated with a suitable singulationprocess.

Since tape substrate 106 receives integrated circuit die, it isimportant for die attach regions 108 of tape substrate 106 to berelatively planar without any bowing or warping before the integratedcircuit die are attached thereto. Bowing and warping problems of dieattach regions 108 proximate each end of tape substrate 106 have beendiscovered using prior auto boating systems. An example of suchsubstrate bowing is illustrated in FIG. 2.

Referring to FIG. 2, the bowing of prior art tape substrate 200 isillustrated. Tape substrate 200 is sandwiched between a boat 201 and aboat clip 202. Typically, the bowing problem occurs because a lateraledge 206 of tape substrate 200 contacts the edges of clip windows 204formed in boat clip 202 as boat clip 202 is positioned over substrate200 during the coupling of boat clip 202 to boat 201 that is supportingtape substrate 200. This is because after tape substrate 200 is placedon boat 201, tape substrate 200 is not totally flat and “coils” upwardalong its longitudinal edges to form a somewhat concave surface. As boatclip 202 is placed on top of tape substrate 200 in order to sandwichtape substrate 200 between boat 201 and boat clip 202, the possibilityof lateral edge 206 getting jammed with clip windows 204 is very high.The present invention addresses this problem by providing, in oneembodiment, tape substrate 106 with a plurality of tabs 300 at each ofits four corners, as described in more detail below in conjunction withFIGS. 3A and 3B.

FIGS. 3A and 3B are plan views of tape substrate 106 according to oneembodiment of the present invention. In embodiment illustrated in FIG.3A, tape substrate 106 includes thirty-six die attach regions 108aligned in three rows and twelve columns; however, any suitable numberof die attach regions 108 may be associated with tape substrate 106 andthey may be arranged in any suitable pattern. Typically, tape substrate106 is formed from polyimide; however, other suitable materials may alsobe utilized for tape substrate 106. Tape substrate 106 is typically cutfrom a larger tape substrate strip and, therefore, includes a pair oflateral edges 302 that are parallel to one another. Tape substrate 106also includes a pair a longitudinal guide strips 304 that are parallelto one another and extend between respective first ends 305 and secondends 306 of lateral edges 302. Longitudinal guide strips typicallyinclude a plurality of apertures 307 formed therein to function asguides for tape substrate 106.

According to the teachings of one embodiment of the invention, eachlongitudinal guide strip 304 includes a pair of tabs 300 exposed atopposite ends thereof As described briefly above, tabs 300 function toprevent substrate bowing and/or warping at the ends of tape substrate106 when boat clip 104 is placed over tape substrate 106 and coupled toboat 102. Typically, the coupling of boat clip 104 to boat 102 ismagnetic coupling; however, other suitable coupling methods may also beutilized. Tabs 300 facilitate the prevention of substrate bowing byacting as guides for each lateral edge 302 of tape substrate 106,thereby substantially eliminating the possibility of contact betweenlateral edges 302 and clip windows 110. Tape substrate 106 essentiallyslides in place when boat clip 104 is pushed downwards onto boat 102without encountering bowing and/or warping of tape substrate 106.

Referring to FIG. 3B, one of the tabs 300 at one end of one of thelongitudinal guide strips 304 is illustrated. As illustrated, tab 300extends beyond a respective plane (denoted by reference number 312) thatis perpendicular to tape substrate 106 and that contains a respectivelateral edge 302 of tape substrate 106. Although tab 300 may have anysuitable shape, in one embodiment, tab 300 is triangularly shaped. In anembodiment where tab 300 is triangularly shaped, tab 300 may be orientedat an angle 314 respect to lateral edge 302 of between approximately 30degrees and 60 degrees. In a particular embodiment, tab 300 may beoriented at an angle 314 of approximately 45 degrees. Because of thenature of how tape substrate 106 is typically formed, tabs 300 generallylie in the same plane as tape substrate 106. Although tab 300 isillustrated in FIG. 3B as being proximate an outer edge 315 oflongitudinal guide strip 304, tab 300 may also be proximate an inneredge 316 of longitudinal guide strip 304 depending on its location ontape substrate 106. For example, also illustrated in FIG. 3B is a tapesubstrate 400 having a lateral edge 402, a longitudinal guide strip 404,and a tab 406 that is disposed proximate an inner edge 408 oflongitudinal guide strip 404. As described above, tape substrate 106 maybe a smaller portion of a larger tape substrate strip formed by cuttingthe longer tape substrate strip laterally into individual tapesubstrates. FIG. 3B illustrates one embodiment of cutting the longertape substrate strip into two separate tape substrates (106 and 400).Therefore, when the longer tape substrate strip is cut, lateral edges302 and 402 are formed in addition to tabs 300 and 406, which in theillustrated embodiment are cut at approximately 45 degree angles withrespect to lateral edges 302 and 402. This not only creates thedesirable tabs 300 and 406, but allows the tape substrate manufacturerto avoid having to lengthen the tape substrate strip that tapesubstrates 106 and 400 are formed from.

The result of cutting the longer tape substrate strip into separate tapesubstrates is illustrated best in FIG. 3A where tabs 300 on the leftlateral edge 302 are proximate inside edge 316 of longitudinal strip 304and tabs 300 on the right lateral edge 302 are proximate outer edge 315of longitudinal guide strips 304. Again, other suitable methods may beutilized to form tabs 300 and, in some embodiments, tabs 300 may beseparate components that are coupled to longitudinal guide strips 304.However, because of the nature of the fabrication of tape substrates,tabs 300 generally are integral with longitudinal guide strips 304.

Thus, in operation of one embodiment of the invention, and withreference to FIG. 1, tape substrate 106 is placed on boat 102. Becauseof the nature of the thickness and type of material that tape substrate106 is formed from, a slight coiling effect results when tape substrate106 is disposed on boat 102. Boat clip 104 is then pushed downwards ontotape substrate 106 and magnetically coupled to boat 102 to secure tapesubstrate 106 therebetween. As boat clip 104 starts to engage tapesubstrate 106, it first contacts longitudinal guide strips 304 andcorresponding tabs 300, which act as guides for lateral edges 302 oftape substrate 106 to eliminate the possibility of contact betweenlateral edge 302 and clip windows 110 to prevent substrate bowing and/orwarping. Integrated circuit die may then be attached to die attachregions 108 and tape substrate 106 without having to worry about anybowing and/or warping that affects the quality/reliability of thecompleted integrated circuits. Although embodiments of the invention andtheir advantages are described in detail, a person skilled in the artcould make various alterations, additions, and omissions withoutdeparting from the spirit and scope of the present invention, as definedby the appended claims.

1. A method for auto-boating, comprising: supporting a tape substrate ona boat, the tape substrate comprising: a pair of lateral edges parallelto one another, each lateral edge having respective first and secondends; a pair of longitudinal guide strips parallel to one another, oneof the longitudinal guide strips extending between the respective firstends of the pair of lateral edges and the other longitudinal guide stripextending between the respective second ends of the pair of lateraledges, each longitudinal guide strip comprising a pair of tabs disposedat opposite ends thereof such that each tab extends beyond a respectiveone of the lateral edges; and coupling a boat clip having a plurality ofwindows to the boat such that the boat clip engages the tabs as the boatclip approaches the boat to ensure that the lateral edges of the tapesubstrate do not engage edges of respective windows proximate thelateral edges.
 2. The method of claim 1, wherein the tabs aretriangularly shaped.
 3. The method of claim 2, wherein the tabs areoriented at an angle of between approximately thirty degrees and sixtydegrees with respect to the respective lateral edge.
 4. The method ofclaim 2, wherein the tabs are oriented at an angle of approximatelyforty-five degrees with respect to the respective lateral edge.
 5. Themethod of claim 1, wherein the tabs lie in the same plane as the tapesubstrate.
 6. The method of claim 1, wherein the tape substrate isformed from polyimide.
 7. The method of claim 1, wherein the tabs areformed integral with the longitudinal guide strips.
 8. The method ofclaim 1, wherein coupling the boat clip comprises magnetically couplingthe boat clip.
 9. A method for auto-boating, comprising: providing atape substrate strip, the tape substrate strip comprising a pair oflongitudinal guide strips and a die attach region disposed between thelongitudinal guide strips; separating the tape substrate strip into aplurality of tape substrates by: cutting the die attach regionperpendicular to the longitudinal guide strips to create one or morelateral edges; and cutting each longitudinal guide strip at an anglewith respect to a respective lateral edge to create one or more tabsextending beyond the respective lateral edge.
 10. The method of claim 9,wherein the angle is between approximately thirty degrees and sixtydegrees with respect to the respective lateral edge.
 11. The method ofclaim 9, wherein the angle is approximately forty-five degrees withrespect to the respective lateral edge.
 12. The method of claim 9,wherein the tape substrate strip is formed from polyimide.